Physics Flashcards
When was the big bang
13.8 billion
When does red-shift happen
When a source is moving away
When does blue shift happen
When a source is moving towards
How do we know our sun contains helium
There are black lines in the spectrum of the light from the Sun where helium has absorbed light
How do we know the universe is moving away from a single point
Light spectra from edge of universe shows red shift
What shift has light from most galaxies been observed to have
Red shift
Which galaxies are moving the fastest
Furthest galaxies
What evidence that universe is expanding
The furthest galaxies move fastest
What shows the universe was once very small
It’s stil expanding
What are galaxies held together by
Gravity
What can stop the expansion of the universe
Gravity between galaxies
What can the presence of dark matter mean
The average density of the universe would be much bigger
How much dark energy is universe made up of
68%
How much of the universe is dark matter made up of
27%
What takes up the remaining 5% of universe
Normal matter
2 main types of telescope
Refracting telescope - lense refract and focus the light
Reflecting telescope - curved mirrors reflect and focus the light
Problems with refracting telescope
Faint Image - some light reflects off the lens
Large lens needed to improve magnification - can be difficult to do
How does reflecting telescope work
Image formed by reflection from a curved mirror
Then magnified by secondary mirror
When/where first telescope invented
Netherlands - 17th century
Optical telescope
observe visible light from space
Optical telescope on the ground
Can only be used at night
Can’t be used if cloudy weather
Radio telescopes
detect radio waves coming from space - can be used in bad weather as radio waves not blocked by clouds
Earth orbiting telescope designed for
designed to relay astronomical data to the earth
Space telescopes
Telescopes in space observe whole sky
Why is moon considered a satellite
Moves around Earth (orbits planet)
Do planets emit visible light
No
What makes a satellite successfully orbit Earth
When its speed is balanced by the pull of Earth’ gravity
Which satellite takes longest to orbit Earth
Moon